It's not just the Ten Commandments that state 'Thou shalt not commit adultery', the Napoleonic civil code in France also insists married couples owe each other fidelity.
So when the website Gleeden, for partnered people who want to have illicit affairs, began promoting extra-marital sex as a "cheap anti-depressant" a Catholic pressure group launched a legal action in France.
The poster shows that Gleeden's grasp of theology might be limited.
It references the Genesis story of Adam and Eve, showing an apple that has been bitten into and highlighting the last four letters of Gleeden. The caption tempts with: "Unlike anti-depressant drugs a lover costs nothing on the state health service."
The poster fails to reference the serpent temptor and makes no reference to the catastrophic consequences for Adam, Eve and indeed all humankind of that single bite. According to the Bible, the Fall led directly to the ejection of the first humans from the Garden of Eden and brought sin into the world.
And while extra-marital sex might for some seem attractive as a temporary cheap anti-depressant as Gleeden says, the poster does not catalogue the emotional cost of adultery, nor the heavy financial toll of divorce. It also fails to mention the attendant difficulties for the celebrity adulterer. Former French presidents who have seen publicity around friends outside marriage include Presidents Hollande, Sarkozy, Chirac, Mitterrand, Giscard and Pompidou.
Jean-Marie Andres, president of Les Associations Familiales Catholiques, which has tabled the legal challenge, said: "We want a legal judgement on an advertising campaign and a website which publicly promotes duplicity, lies and violation of the law." He added: "The drastic social consequences of infidelity cannot be ignored by our common conscience."
Gleeden has more than 2.3 million members in Europe, including about a million in France.
Spokeswoman Solène Paillet said: "We do not encourage anyone to cheat on their partner. We just provide a platform. There are people who find personal fulfilment in having someone else in their life."
Last year, Gleeden revealed the top ten fragrances worn by adulterers.Top of the table for women was Shalimar by Guerlain and second was Coco Mademoiselle by Chanel.
A separate study in the Journal of Sex Research found that people with a high-powered job were more likely to be unfaithful.
Social Psychologist Dr Joris Lammer surveyed more than 600 heterosexual Dutch men and women on the Men's Health and Marie Claire websites and found that fewer than one in ten people in lower management had been unfaithful while nearly one in four of those in the top jobs had cheated.
